The present invention relates to hydrocarbon processing in general and more particularly, to treating the product from a catalytic hydroprocessing or catalytic reforming process to increase the yield of liquid products. The present invention, therefore, is essentially a combination process for the upgrading of reformates and hydroprocessed products which employs a two-zone scheme and certain intermediate pore size essentially alumina-free zeolitic materials.
A combination process for the upgrading of a naphtha charge employing a particular sequence of catalyst compositions is described in U.S. Pat. No. 3,849,290 to Wise et al., incorporated by reference herein. In that process, a naphtha charge is reformed with a platinum reforming catalyst under reforming conditions to produce an aromatic-enriched product effluent comprising normal and branched hydrocarbons. The product of the reforming process is then contacted with a ZSM-5 type of crystalline aluminosilicate zeolite catalyst composition to selectively crack singly branched and normal hydrocarbons comprising C.sub.7 and higher boiling hydrocarbons. Thereafter, the product of the selective cracking is contacted with a crystalline aluminosilicate zeolite hydrocracking catalyst of the erionite type under temperature and pressure conditions selected to crack n-paraffins without substantial cracking of multi-branched hydrocarbons.
U.S. Pat. No. 3,380,911 to Owen relates to a method and system for effecting catalytic cracking of relatively high boiling hydrocarbon feed materials by sequential contact with a plurality of catalyst composition of significantly different activity levels. In that method, a hydrocarbon feed material is combined with a first relatively high activity fluidizable catalytic material of relatively small particle size containing aluminosilicate constituents of water crystal structure to form a slurried mixture. Thereafter, the mixture along with vaporous material is combined with catalyst particles of significantly lower catalytic activity and passed as a dispersed mass through a second catalytic conversion zone. The second conversion zone is maintained under temperature conversion conditions in the range of from about 800.degree. to about 1100.degree. F. so that it may be equal to or higher than the temperature employed in the first conversion step comprising the limited conversion step with the higher activity aluminosilicate-containing catalyst. In other words, the cracking zone containing the most active cracking catalyst is maintained at a substantially lower temperature than the zone containing the lower activity catalyst particles.